Process of producing composite or coated articles comprising foamed plastics and covering layers



U ted Stat Pawn 6 moonss or r zonucnvc. COMPOSITE oR COATED ARTICLES COMPRISING FOAMED. PLASTICS. AND: COVERING LAYERS Peter- 'Hoppe, Troisdorf, Germany, assignor,by.direct and meme assignments, of; one-halfto: Farbenfabrlken Bayer AktiengesellSchaft,-l Lcverkusen', ,Germany, a cor- "poration' ofrGermany, .and one-half to :Mobay Chemical Company, Pittsburgh, Pa., a corporation of Delaware.

NoDi'aWiiig'. Application Feb u y! 1955 Serial No. 485,820

Claims-priority, application. Germany February 9,1954

11 Claims; (Cl; 181-'-60)- This invention relates to: composite or. coated articles comprising plastic foams and. covering layers, and to. a process of producing sameg.

It is old in theiartztoapply. synthetic-resinsto plastic foams-fort thetpurpose.:offproducing composite orv coated articles. Howevergtit is: exceedinglydifiicult to coat or lacquer such plastic foams in moldedfform so as to providersame -withia smooth and impervious surface,- particularly; when1such' molded materials have: hi ghly irregular surfaces or'contplicated:contours.

Therefore, it is an object of the present invention to overcome: the: above 1 difliculty: and provide: an-improved processizof-iproducing composite: or coated articles 1 comprising; a; plastic foam and t a smooth K impervious outer covering layer.

Another-tobject of the invention to provide an economically 'andrcommerciallyv practical process of producingrmoldedrcomposite or coated zarticles comprising ;a plasticcfoam having highly, irregular surfacesor complicated; contours; which: are coated; or covered with a smooth and? impervious outerlayer.

Other. objects and advantages of the. invention will aPpsar hereinafter: as-the: description proceeds.

In accordance with the present invention, composite or coated articles comprising plastic foams and covering layers are-prepared. by, applying to a suitable. surface a covering layer of the desired thickness comprising a polyester-isocyanate mixture=- and, if desired, a solvent or diluentandthen, prior to or after cross-linking. or curing such mixture,,coating this layer with.apolyester-isocyanatetmiirture. which produces a plastiofoam.

The covering layers may be produced by casting or sprayingthe:polyester-isocyanate. mixture intotat mold. Thesecovering layers may bereinforced by, means of fabric'stintroduced into the mold before. the addition of polyester-isocyanate mixture. As reinforcing agents for the covering layers, fibrous materials consisting of glass, synthetic resins, polyamides or wire, etc. may be employed. The fabric or fibrous materials are impregnated by the reactive polyester-isocyanate mixture and on solidification of the latter are rigidly bonded to the films constituting the covering layers.

Polyesters which are suitable for preparing the covering layers may be prepared from adipic acid and diand/ or trihydric alcohols, using such a ratio of the reactants that the resultant polyester has a hydroxyl number within the range of about 20 to about 350. Diisocyanates which may be reacted with these polyesters to form the covering layer include, inter alia, hexamethylene diisocyanate and toluylene diisocyanate.

The covering layer may be produced from a plurality of layers or coatings which have varying thicknesses. The final coating or covering layer serves only as a bonding layer and therefore can be kept quite thin. In

general, the single layers will havea thickness within the,

range of about20.2 mm. to about :15 mm.

The plastic foam applied to the coveringlayermay be prepared from any polyester commonly employed in the production of polyester-based foamed plastics. These polyesters'areusually derived-from dicarboxylic acids, such as adipic acid and phthalic acid; anddi-and/or trihydric alcohols, such as:ethylene-glycol, diethylene glycol, butyleneglycol-L3, glycerol, trimethylol propane and hexanetriol. The diisocyanate most suitabl'for the reaction withthese polyestersto produce plastic foams is toluylene diisocyanate, although otherpolyism cyanates may be used, if desired.-

Depending. upon the-nature of the polyesters and diisocyanates used in the foaming process; either elasticpor rigid foams-are obtained in combintation withthe coveringylayer.

In the preparation of the covering layer, cross-linking,

may be effected by allowing the pretreated molds to stand inthe-open air for a certain period, the water vapor contained in the airacting: as the cross-linkingagent. Alternatively, the molds into which the polyester-isocyanate mixture has been cast or sprayed to formacovering layer, may: be treated with steam to bring about crosslinking. A third option is to carry out-the-= foaming processimm'ediately afterv casting-or spraying-the polyester-isocyanate mixture serving to build up, the-covering layer into the mold, the heat-and the steam evolved inthe foaming process bringing-aboutcrosselinking of the initial mixture used in forming the covering-layer.

For a more complete understanding of the present invention, reference is.made to the following illustrative examples, in which the parts and percentages are by weight.

Example-1 Into a degreased mold there is sprayed a 20% methylene chloride solution ofa compositionconsisting of the addition productof 100 parts ofa linear adipic acid diethylene glycol polyester (hydroxyl number: and 13 partsof hexamethylene diisocyanate, .and-2.5% of. a mixture of peralkylated'diethylene triamine and peralkylated triethylene tetramine, based on the weight of said addition product. After carrying out-this operation, 100 parts of an hydroxyl polyester'of-adipic' acid and ethylene glycol (hydroxyl number: 25 parts of toluylene diisocyanate and 7 parts of an activator mixture consisting of 3 partsof the ester of 1 mol ofadipic acid and 2 mols of N-diethyl ethanolamine, 2 parts of dispersing agent and 1.2 parts of water are intimately mixed and the resulting foamable composition introduced into the pretreated mold. During the ensuing foaming process, the foamed product is intimately combined with the covering layer'or coating initially sprayed'into the mold;

Example 2 The procedure described in Example 1 is repeated using in the initial methylene chloride spray the addition product of parts of a linear adipic acid-glycol polyester and 5 parts of a triisocyanate such as triphenylmethane triisocyanate or the triisocyanate derived from 1 mol of hexanetriol and 3 mols of toluylene diisocyanate. This yields a composite article in which the covering layer is rigidly bonded to the polyurethane foam.

Example 3 The procedures described in Examples 1 and 2 are followed except that a nylon fabric is introduced after the initial spraying operation. This yields composite articles having a covering layer of substantially improved surface strength.

Example 4 The procedures described in Examples 1 and 2 are repeated using a dyestutf in the initial spray. A highly satisfactory dyeing efiect -'is obtained in the covering layers with only 0.54% of dyestuif, based on the weight of the covering layer.

' Example 5 The procedures described in Examples 1 and 2 are followed except that a plurality of spraying operations are carried out and each sprayed film or layer is cured or cross-linked before applying the next layer. A com posite article consisting of a layer of plastic foam and a relatively thick polyurethane coating or covering layer is thereby obtained.

Example 6 The spraying operation is carried out with a 20% methylene chloride solution of a mixture consisting of 100 parts of the polyester obtained from 15.6 mols of adipic acid, 16.3 molsof diethylene glycol and 1.0 mol of trimethylol propane (hydroxyl number of said polyester: 60), and 9.2 parts of toluylene diisocyanate. In the foaming process, there are used 100 parts of a polyester mixture consisting of 50 parts of a polyester obtained from 5,1 mols of adipic acid, 1.0 mol of phthalic anhydride and 8.4 mols of hexanetriol and 50 parts of a polyester obtained from 1.43 mols of adipic acid, 1.0 mol of hexanetriol and 1.0 mol of 1,3-butanediol, 45 parts of toluylene diisocyanate, 1 part of hexahydrodimethyl-aniline and 10 parts of calcium silicate containing about 10% of water.

In carrying out the process of this invention, the polyester-isocyanate mixture, with or without a suitable dye, is diluted with methylene chloride, benzene toluene or another diluent or solvent until it can be sprayed. When the sprayable composition is introduced, it is distributed in the light metal molds which must be highly polished in order to produce molded elements with a smooth surface. For accelerating the evaporation of the solvent, it is desirable to briefly irradiate with infrared light the applied solution of the polyester-isocyanate mixture.

When separable molds are employed, the process permits the provision of a completely impervious covering layer on the foamed plastic if the surfaces of the halves of the mold which are in contact are additionally provided with a polyester-isocyanate layer after the initial polyester-isocyanate layers have been applied by spraying.

The process of the instant invention is useful for producing molded articles of all kinds such as plates, dolls, lifebeltsand life buoys having smooth impervious coatings or covering layers.

What is claimed is:

a 1. A process of producing coated polyurethane foams which comprises forming, on a surface, a layer comprising a polyester-isocyanate mixture dissolved in an inert 7 organic solvent therefor, evaporating substantially all of said solvent, applying to the resulting layer a foaming composition comprising a polyester-isocyanate mixture, and carrying out the foaming operation.

2. The process of claim 1- wherein said polyesterisocyanate dissolved in said solvent is cross-linked with water prior to the application of said foaming composition.

3. The process of claim 1 wherein said polyesterisocyanate dissolved in said solvent is cross-linked with water after the application of said foaming compositiorn 4. A process of producing coated polyurethane foams as defined in claim 1, in which the layer of the first mentioned mixture is formed by casting same in a mold.

5. A process of producing coated polyurethane foams as defined in claim 1, in which the layer of the first mentioned mixture is formed byspraying same in a mold.

6. A process of producing coated polyurethane foams as defined in claim 5, in which a fibrous reinforcing material is introduced into the mold prior to the layer of the said first mentioned mixture.

7. A process of producing coated polyurethane foams as defined in claim 1, in which the polyester-isocyanate mixture used in the preparation of said layer contains a tertiary amine as an accelerator.

8. A process of producing coated polyurethane foams as defined in claim 1, in which the polyester-isocyanate mixture used in the preparation of said layer is diluted with methylene chloride.

9. A process of producing coated polyurethane foams as defined in claim 1, in which the polyester-isocyanate mixture used in the preparation of said layer contains a dye.

10. A process of producing coated polyurethane foams as defined in claim 1, in which the first mentioned layer is formed by a plurality of applications of said polyesterisocyanate mixture.

11. In the coating of a cellular polyurethane, the improvement which comprises coating a mold with a solution of a polyurethane in a suitable inert organic solvent therefor, evaporating substantially all of said solvent, placing a foamable polyurethane reaction mixture adjacent the resulting coating and effecting foaming thereof, thereby securing the resulting cellular structure to the coating while avoiding appreciable penetration of the cellular structure by the coating.

References Cited in the file of this patent UNITED STATES PATENTS Verela Feb. 19, 

1. A PROCESS OF PRODUCING COATED POLYURETHANE FOAMS WHICH COMPRISES FORMING, ON A SURFACE, A LAYER COMPRISING A POLYESTER-ISOCYANATE MIXTURE DISSOLVED IN AN INERT ORGANIC SOLVENT THEREFOR, EVAPORATING SUBSTANTIALLY ALL OF SAID SOLVENT, APPLYING TO THE RESULTING LAYER A FOAMING COMPOSITION COMPRISING A POLYESTER-ISOCYANATE MIXTURE, AND CARRYING OUT THE FOAMING OPERATION. 